All those different models you see in the E5v3 product line aren't separate products, they're bins of probably just 2-3 different CPUs. Many of the chips made will have defects, and the number of working cores, their maximum stable frequency, and their thermal properties determine which product number they get sold as. Amazon probably just gets one of these bins: the chips that come out of testing meeting their specs are sold to them as a 2676. Intel doesn't actually have to custom design any hardware.